(1) Field of the Invention
The invention relates to a boring appliance for producing a concrete element in the ground with a vehicle.
A boring appliance of this type is known from JP 56 031 928 A, in which in addition to the boring tool a complete preparation and mixing installation for concrete are placed on a carriage.
(2) Description of Related Art
In the case of loose soil, in ground water or for concrete piles, which are to be produced in displaceable soils, preferably the following production procedures are used:                boring methods using continuous, long soil augers,        displacement boring methods, in which essentially long tubes are turned or rammed into the ground, the cropping out ground being displaced to the side,        methods in which long soil augers are surrounded with a rotary encasing tube and both the auger and the tube are simultaneously introduced into the ground.        
Such methods are essentially based on the same concreting procedure. After the augers or enveloped augers or displacement tubes have been brought to the final depth, the tube and/or auger is retracted and during retraction concrete is pumped into the resulting space or cavity through inside or soil-sided openings in the auger or tube. The introduction of concrete preferably takes place under a low pressure to ensure that no soil from the borehole wall can pass into the cavity.
The use of pumpcrete has a positive effect on the production rate of such piles.
According to the prior art, such as is e.g. known from U.S. Pat. No. 3,255,592, the concreting of such piles takes place in that at the outside or air-sided end of the boring tool, i.e. either at the outside end of the continuous auger or at the outside end of the displacement tubes, a concreting hose is fixed and leads to a concrete pump which is supplied by mobile or travelling mixers. As the concreting head at the end of the concreting auger or tube is constantly moved up and down, it is not recommended that working takes place with a freely hanging hose. During each pump impact the hose is struck and swings through the air. This can easily lead to damage and constitutes a hazard for personnel.
Thus, generally mobile concrete pumps with adjustable distributing masts or towers are chosen. This procedure is practicable in principle, but suffers from the disadvantage that throughout the pile production time it is necessary to have at the building site and expensive concrete pump with adjustable distributing mast, including driver, although the actual concreting process only lasts for a short time.
To economize on the driver, constructions are known such as from U.S. Pat. No. 6,048,137, in which a stationary concrete pump is installed at the building site and from there hoses are laid up to the concreting head on the boring appliance. Since as a result of the rapid operation the boring appliance covers considerable distances, relatively long hoses are used, which in the case of considerable heat suffers from the disadvantage that in such long hoses frequently blockages occur due to overheating. A further risk is that such hoses can be damaged during the movement of the boring appliance. The generally concrete-filled hoses are heavy and are therefore difficult for the site personnel to handle during the movement of the boring appliance. It must constantly be ensured that the hoses are not bent or that the tracked travelling gear does not pass over the hoses.
As a result of the pressure surges of the plunger or piston pumps the hose on the ground scrapes on the substrate, which leads to damage to the hose casing or jacket.
U.S. Pat. No. 5,967,700 discloses a boring appliance with pressure containers on the top of a superstructure from which pulverulent materials or water are injectable directly into the borehole for producing concrete therein.